The ability to grow various types of thin films at low temperatures, i.e., less than about300 .degree. C., is of increasing importance. Thin films of, e.g., rhodium and iridium, are useful in oxidative protection applications, as reflective coatings for mirrors in optics, and in the micro-electronics industry.
Iridium films have been previously deposited using iridium halides and molecular hydrogen. Iridium films have also been deposited on silicon using laser stimulated deposition from gaseous and condensed iridium tris(acetylacetone).
Rhodium films have been prepared by sputtering techniques, vacuum deposition techniques, and by a technique involving the thermal decomposition of [Rh(CO).sub.2 Cl].sub.2. Rhodium films have also been deposited by a plasma-enhanced chemical vapor deposition process as described by Espuler et al., Appl. Phys. A 48, 373-375 (1989). In that process, a single gaseous stream including an inert carrier gas, the organometallic precursor compound, i.e., dicarbonyl-2,4-pentationato-rhodium, and hydrogen gas is passed into a parallel plate reactor wherein a plasma is generated.
However, many of the previous methods generally suffer from the need for excessively high substrate temperatures thereby preventing the use of a temperature sensitive substrate, or suffer from low deposition rates. In addition, metal films produced by some of the previous methods have been inferior films in terms of: (a) purity due to either carbon or halide contamination; (b) morphology as such films typically are either amorphous or polycrystalline (i.e., a wide variety of crystal sizes) in structure; or (c) stability of the resultant film due to internal stresses within the material. Carbon contamination of films produced from organometallic precursors has generally been a major problem.
Accordingly, it is an object of this invention to achieve a low temperature chemical vapor deposition process allowing for the production of highly pure thin films of, e.g., rhodium, iridium, molybdenum, tungsten, rhenium, platinum, or palladium on temperature sensitive substrates, e.g., plastics or semiconductors.
Another object of this invention is to provide a highly pure nanocrystalline film of rhodium, iridium, molybdenum, tungsten, rhenium, platinum, or palladium, such film substantially free of carbon contamination.
Still another object of this invention is to provide an article including a temperature sensitive substrate having a thin film of iridium or rhodium coated thereon.
It is yet a further object of this invention to provide a process capable of reducing the carbon contaminant content of a metallic film prepared from one or more organometallic precursor compounds.